Kelly told SI's Peter King earlier this week that he had "countless microscopic" tumors in his head and thus was not a candidate for surgery.

Instead, he faces a intensive seven-week series of chemotherapy and radiation treatments that will take place nearly five days a week.

Despite the aggressive treatment, Kelly's doctor is optimistic and says the cancer is "very treatable and potentially curable."

"I just know there’s a lot of work to do, to shrink the cancer," Kelly said. "I just pray it works. If you hear I’m about to have surgery, then you know it’s working. That’s the goal. But it won’t be an easy operation.”